redhedlvr2

There's a good tutorial here (at least it looks like a good one--and Lifehacker is an awesome site besides). I've never installed one, but I've watched my son (the one who DIDN'T go to school for computers) install one in about ten minutes. It looks harder than it actually is, just from observation. Although the inside of a computer like yours may be more alien than the norm, given its mashed-together origins. ;)